The invention relates generally to novel secondary amine-functional silanes, which have application in, for example, moisture-curable polymers, silane-terminated polymer dispersions, and cured polymers derived therefrom.
Compounds containing more than one type of functional group are often referred to as multifunctional compounds. The type of functional groups determines the properties and applications of the compounds. When multifunctional compounds contain moisture-curable functional groups such as alkoxysilane groups, for example, the multifunctional compounds are useful in applications where polymer curing is effected by exposure of polymers containing the multifunctional compounds to moisture. Alkoxysilane groups can form siloxane (xe2x80x94Sixe2x80x94Oxe2x80x94Sixe2x80x94) linkages in the presence of atmospheric moisture. Siloxane linkages not only form a polymer network, but they also improve adhesion of the polymers to non-porous surfaces, such as glass.
Multifunctional compounds containing moisture-curable functional groups have found use in many applications. For example, U.S. Pat. No. 5,587,502 describes the use of multifunctional compounds in the preparation of moisture-curable adhesives, sealants (e.g., automobile seam sealants), putties, and the like. The multifunctional compounds therein comprise both hydroxy and alkoxysilane moieties. The hydroxy functionality can react with isocyanate-functional materials to form alkoxysilane-functional polyurethanes. See also, PCT Publication No. WO98/18844, wherein multifunctional compounds comprising both hydroxy and alkoxysilane moieties are reacted with an isocyanate-functional poly(ether-urethane) to form an alkoxysilane-functional poly(ether-urethane). The cured compositions therefrom are also particularly useful as sealants.
U.S. Pat. No. 5,717,125 discloses a wide variety of multifunctional compounds that are both hydrolyzable and polymerizable to form both inorganic and organic networks, respectively, throughout the resulting composition. The compositions therein are purportedly particularly useful in dental applications. However, it is not always desirable to include polymerizable groups in the multifunctional compounds.
Multifunctional compounds bearing both amine and alkoxysilane moieties are well known. See, for example, U.S. Pat. Nos. 3,033,815; 3,627,722; 3,632,557; 3,700,716; 3,979,344; 4,067,844; 4,209,455; 4,628,076; 4,718,944; 4,857,623; 5,174,813; and 5,364,955. Both primary amine-functional alkoxysilanes and secondary amine-functional alkoxysilanes are described therein.
Primary amine-functional alkoxysilanes are often extremely reactive with a variety of electrophiles (e.g., isocyanates, oxirane rings, and anhydrides), resulting in strongly hydrogen-bonded products. For example, the reaction of primary amines with isocyanates is extremely fast and produces dihydrourea linkages. Dihydrourea linkages may disadvantageously increase product viscosities, however, which can hinder processability of the product, subsequent mobility of attached functional groups and reactivity of attached functional groups. Additionally, fast reaction rates, often associated with primary amine-functional alkoxysilanes, are undesirable in many applications. For example, uncontrollable reaction rates can lead to excessive generation of heat, fast gel times, and decreased reaction selectively.
In general, secondary amine-functional alkoxysilanes react more slowly with electrophiles than do the corresponding primary amine-functional alkoxysilanes. Furthermore, hydrogen bonding in their adducts is significantly reduced or eliminated. Examples of commercially available secondary amine-functional silanes include: 3-(N-phenyl)aminopropyltrimethoxysilane; 3-(N-methyl)aminopropyltrimethoxysilane; and 3,3xe2x80x2-iminobis(propyltrimethoxysilane). Methods of preparation are described in U.S. Pat. No. 3,632,557. However, costs of such secondary amine-functional alkoxysilanes, often twice those of their primary amine analogs, limit their commercial application.
U.S. Pat. Nos. 3,033,815 and 4,067,844 disclose secondary amine-functional alkoxysilanes that are formed by a Michael-type reaction of primary amine-functional alkoxysilanes with (meth)acrylate or (meth)acrylonitrile Michael-type receptors. Although these methods produce secondary amine-functional alkoxysilanes at relatively low cost, the reaction products are contaminated with varying quantities of primary and tertiary amine-functional alkoxysilanes.
Preparation of N-alkoxysilylalkyl-aspartic acid diesters from certain amino-alkyl alkoxysilanes and maleic or fumaric acid esters is disclosed in U.S. Pat. No. 5,364,955. These N-alkoxysilylalkyl-aspartic acid diesters react with isocyanates, however, to form polymers containing urea and ester groups. The polymers are reportedly unstable, however, with the urea groups cyclizing to hydantoins (See U.S. Pat. No. 5,756,751). This reaction is illustrated below, wherein X, Z, R, R2, R3, R4, n, and m are as defined therein: 
As can be seen from the reaction diagram, during cyclization, alcohol is expelled as a by-product. Expelled alcohol can be problematic since it may undesirably slow subsequent moisture-cure of the alkoxysilane moieties. Furthermore, hydantoin formation may lead to undesirable shrinkage of the resulting polymer. See also European Pat. Application No. 0 831 108 Al, which discloses N-alkoxysilylalkyl-aspartic acid diesters and polyurethane products therefrom, which polyurethane products are reportedly useful as sealants.
While many multifunctional compounds, particularly secondary amine-functional silanes are known, a further variety of compounds would be desirable to enable tailorability for certain applications. For example, secondary amine-functional silanes that are stable without cyclizing to form hydantoins are desirable for use in applications where shrinkage, for example, from hydantoin formation is undesirable. One such application is the field of sealants, like automobile seam sealers. Furthermore, cost-effectiveness is also generally a consideration when selecting suitable multifunctional compounds for formulating compositions.
Secondary amine-functional silanes of the present invention are preparable at lower costs than many conventional secondary amine-functional silanes and resist hydantoin formation. Furthermore, methods for their preparation result in relatively pure reaction products. That is, other reaction products, such as primary or tertiary amine-functional silanes, for example, are minimized or eliminated.
In one embodiment, secondary amine-functional silanes of the present invention include chemical compositions of Formula I: 
wherein:
X comprises at least one silane group; and
Y comprises a hydrocarbon backbone, at least one amide group on an xcex1-carbon, and at least one ester group on a B-carbon with respect to N. In preferred embodiments, Y contains only one ester group and/or Y is ethylenically saturated. In a further embodiment, Y is ethylenically saturated and contains only one ester group.
A particularly preferred secondary amine-functional silane of the present invention corresponds to that of Formula II: 
wherein:
n is 1, 2 or 3, preferably 3;
R1 is a divalent linking group;
Each R2 is independently a monovalent organic radical;
Each R3 is independently a monovalent organic radical;
R4 is a monovalent organic radical;
R5 and R6 are each independently selected from the group consisting of hydrogen and monovalent organic radicals or R5 and R6, when taken together, may form a 5- or 6-membered ring with the nitrogen atom;
R7 is selected from the group consisting of hydrogen and monovalent organic radicals; and
R8 is selected from the group consisting of hydrogen and monovalent organic radicals.
Preferably, R1 is selected from the group consisting of linear and branched alkylene groups having 1 to about 6 carbon atoms. More preferably, R1 is a propylene group.
Preferably, each R2 is independently selected from the group consisting of linear and branched alkyl groups having 1 to about 6 carbon atoms. More preferably, each R2 is independently selected from the group consisting of a methyl group and an ethyl group.
Preferably, each R3 is independently selected from the group consisting of linear and branched alkyl groups having 1 to about 6 carbon atoms. More preferably, each R3 is independently selected from the group consisting of a methyl group and an ethyl group.
Preferably, R4 is an alkyl group having 1 to about 6 carbon atoms. More preferably, R4 is selected from the group consisting of a methyl group and an ethyl group.
Preferably, R5 is selected from the group consisting of hydrogen and alkyl groups having 1 to about 6 carbon atoms. More preferably, R5 is hydrogen.
Preferably, R6 is selected from the group consisting of an alkyl group having 1 to about 6 carbon atoms and an aryl group. More preferably, R6 is an alkyl group.
Preferably, R7 is selected from the group consisting of hydrogen and alkyl groups having 1 to about 6 carbon atoms. More preferably, R7 is hydrogen.
Preferably, R8 is selected from the group consisting of hydrogen and alkyl groups having 1 to about 6 carbon atoms. More preferably, R8 is hydrogen.
The secondary amine-functional silanes are also useful for preparing moisture-curable silane-functional polymers derivable therefrom. Cured polymers are also derivable from such polymers.
In one embodiment, a moisture-curable silane-functional polymer corresponds to that of Formula III: 
wherein P is an organic group having a molecular weight of at least about 15 and a valence of x, wherein x is an integer greater than or equal to 1. X and Y are as defined above.
In a particularly preferred embodiment, a moisture-curable silane-functional polymer corresponds to that of Formula IV: 
wherein P is an organic group having a molecular weight of at least about 15 and a valence of x, wherein x is an integer greater than or equal to 1. R1-R8 and n are as defined above.
The secondary amine-functional silanes are also useful for preparing silane-terminated polyurethane dispersions derivable therefrom. Cured polymers are derivable from such dispersions.
Secondary amine-functional silanes of the present invention and polymers therefrom are useful in preparing composites and other articles. For example, composites comprise a substrate and a layer of moisture-curable silane-functional polymer coated thereon. The polymers can be cured to provide composites comprising a substrate and a layer of cured polymer derived from the moisture-curable silane-functional polymer coated thereon. The secondary amine-functional silanes are also particularly useful for forming coatings, adhesives, elastomers, and sealants, such as automobile seam sealants.
Also disclosed is a method of preparing secondary amine-functional silanes of the present invention. The method comprises the step of reacting a primary amine-functional silane having the structure: 
with one or more amide-ester Michael-type receptors having the structure: 
wherein:
n is 1,2 or3;
R1 is a divalent linking group;
Each R2 is independently a monovalent organic radical;
Each R3 is independently a monovalent organic radical;
R4 is a monovalent organic radical;
R5 and R6 are each independently selected from the group consisting of hydrogen and monovalent organic radicals or R5 and R6, when taken together, may form a 5- or 6-membered ring with the nitrogen atom;
R7 is selected from the group consisting of hydrogen and monovalent organic radicals; and
R8 is selected from the group consisting of hydrogen and monovalent organic radicals.
In general, secondary amine-functional silanes of the present invention comprise an ester group and an amide group. The secondary amine-functional silanes can be represented by Formula I: 
wherein:
X contains at least one silane group; and
Y comprises a hydrocarbon backbone, at least one amide group on an xcex1-carbon, and at least one ester group on a xcex2-carbon with respect to N. As understood by one of ordinary skill in the art, the xcex1-carbon atom is the first carbon adjacent N and the xcex2-carbon atom is the second carbon adjacent N.
In a preferred embodiment, the ester group is a terminal group of the hydrocarbon backbone. It is believed that increasing the distance between the amine and ester groups also minimizes and typically prevents hydantoin formation or subsequent cyclization.
In another preferred embodiment, Y contains only one ester group. By reducing the number of ester groups in the multifunctional compound, hydantoin formation or subsequent cyclization is even further minimized or eliminated.
In yet another preferred embodiment, Y is ethylenically saturated. As such, the secondary amine-functional silane does not contain polymerizable groups, which polymerizable groups may not be desirable for certain applications.
Most preferably, Y contains only one ester group and Y is ethylenically saturated. For example, preferred secondary amine-functional silanes of the invention are those of Formula II: 
wherein:
n is 1,2 or3;
R1 is a divalent linking group;
Each R2 is independently a monovalent organic radical;
Each R3 is independently a monovalent organic radical;
R4 is a monovalent organic radical;
R5 and R6 are each independently selected from the group consisting of hydrogen and monovalent organic radicals or R5 and R6, when taken together, may form a 5- or 6-membered ring with the nitrogen atom;
R7 is hydrogen or a monovalent organic radical; and
R8 is hydrogen or a monovalent organic radical.
It is believed that the structure of Y minimizes and typically prevents hydantoin formation or subsequent cyclization.
Monovalent organic radicals include, for example, hydrocarbon groups (e.g., linear or branched alkyl groups, alkenyl groups, cycloalkyl groups, or aryl groups) that may, optionally, contain one or more heteroatoms (e.g., oxygen, nitrogen, sulfur, silicon, and the like), functional groups (e.g., carbonyl groups, halo groups, nitro groups, cyano groups, alkoxy groups, thio groups, amino groups, ester groups, aryl groups, silane groups, and the like), or combinations thereof. Typical monovalent organic radicals include hydrocarbon groups having from about 1 to about 20 carbon atoms, preferably from about 1 to about 12 carbon atoms, more preferably from about 1 to about 8 carbon atoms.
Divalent linking groups can be, for example, linear or branched hydrocarbon groups. Typical divalent linking groups include hydrocarbon groups having from 1 to about 20 carbon atoms, preferably from about 1 to about 12 carbon atoms, more preferably from about 1 to about 8 carbon atoms, optionally containing one or more heteroatoms (e.g., oxygen, nitrogen, sulfur, silicon, and the like), functional groups (e.g., carbonyl groups, halo groups, nitro groups, cyano groups, alkoxy groups, thio groups, amino groups, ester groups, aryl groups, silane groups, and the like), or combinations thereof.
Particularly preferred compounds of Formula II are those embodiments wherein:
R1 is a linear or branched alkylene group having 1 to about 6 carbon atoms, more preferably a propylene group;
Each R2 is independently a linear or branched alkyl group having 1 to about 6 carbon atoms, more preferably a methyl group or an ethyl group;
Each R3 is independently a linear or branched alkyl group having 1 to about 6 carbon atoms, more preferably a methyl group or an ethyl group;
R4 is an alkyl group of 1 to about 6 carbon atoms, more preferably a methyl group or an ethyl group;
R5 is hydrogen or an alkyl group of 1 to about 6 carbon atoms, more preferably hydrogen;
R6 is an alkyl group of 1 to about 6 carbon atoms or an aryl group, more preferably an alkyl group, for example t-butyl;
R7 is hydrogen or an alkyl group of 1 to about 6 carbon atoms, more preferably hydrogen;
R8 is hydrogen or an alkyl group of 1 to about 6 carbon atoms, more preferably hydrogen; and
n is 2 or 3, more preferably 3.
The secondary amine-functional silanes of the invention may be formed by any suitable method. Preferably, due to the relatively lower cost thereof, the secondary amine-functional silanes are prepared by reaction of one or more primary amine-functional silanes with various amide-esters. For example, the secondary amine-functional silanes are preparable by reacting primary amine-functional silanes having the structure: 
wherein R1, R2, R3, and n are as defined above, with one or more amide-ester Michael-type receptors having the structure: 
wherein R4-R8 are as defined above.
The amide-ester Michael-type receptors may be formed by any of a number of suitable methods. Useful amide-ester Michael-type receptors include, for example, adducts of alcohols with isomaleimides. The use of an organotin salt as a catalyst may increase the yield of such a reaction. For example, the reaction of an isomaleimide with an alcohol can be carried out at from about 0xc2x0 C. to about 100xc2x0 C., preferably from about 22xc2x0 C. to about 70xc2x0 C. Examples of organotin salts useful as catalysts include: dibutyltin laurate, dibutyltin diacetate, dimethyltin dilaurate, stannous octoate, bis(lauryldibutyltin)oxide, and dibutyltin dimercaptide. A preferred catalyst is dibutyltin diacetate. The amount of catalyst used may vary from about 0.1 to about 10 mol % based on the amount of alcohol.
An alternate method of preparing amide-ester Michael-type receptors includes reacting maleic anhydride with an amine followed by converting the resulting carboxylic acid group to an ester. These methods are described in co-pending U.S. patent application having Ser. No. 09/109,588 now U.S. Pat. No. 6,005,062. Other methods are readily recognizable by those of ordinary skill in the art.
Any suitable primary amine-functional silane may be used in the preferred method. Many primary amine-functional silanes are commercially available and are relatively inexpensive raw materials. Useful primary amine-functional silanes include, for example, 3-aminopropyltriethoxysilane; 3-aminopropyltrimethoxysilane; 3-(2-aminoethyl)aminopropyltrimethoxysilane; 3-aminopropylmethyldiethoxysilane; 3-aminopropyltris(2-(2-methoxyethoxy)ethoxy)silane; 3-aminopropyltriisopropenyloxysilane; 3-aminopropyltri(butanone oximo)silane; 4-aminobutyltriethoxysilane; N-2-(aminoethyl)-3-aminopropyltris(2-ethylhexoxy)silane; 3-aminopropyldimethylethoxysilane; 3-aminopropyldiisopropylethoxysilane; and 3-aminopropylphenyldiethoxysilane. 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane are preferred.
The reaction of a primary amine-functional silane with an amide-ester Michael-type receptor is often spontaneous, rapid, and nearly quantitative. Accordingly, the secondary amine-functional silanes may be synthesized, for example, by simply allowing mixtures of primary amine-functional silanes and amide-ester Michael-type receptors to stand overnight at 70xc2x0 C. in the absence of catalyst.
The reaction generally proceeds to 95-99% completion within about 24 hours. Hydrogen, carbon, and silicon nuclear magnetic resonance spectroscopy (1H-NMR, 13C-NMR, and 29Si-NMR, respectively) are useful in confirming structures of the reaction products. Since the reactions are essentially clean (i.e., the reaction products include less than about 5 weight % products other than secondary amine-functional silanes, typically essentially no products other than secondary amine-functional silanes), purification of the reaction products is generally not required, which may be advantageous for certain applications.
The secondary amine-functional silane compounds of the present invention can be reacted with other compounds. For example, the secondary amine-functional silane compounds can be reacted with compounds having electrophilic groups. Such electrophilic groups include, for example, isocyanate groups, oxirane rings, and anhydride groups. Included within the scope of this invention are silane-functional polymers obtained by reacting the secondary amine-functional silanes with organic groups reactive therewith. These silane-functional polymers are then moisture-curable to form a polymer network containing siloxane linkages.
Preferably, the secondary amine-functional silane compounds are reacted with compounds containing at least one isocyanate group. As such, a preferred silane-functional polymer resulting therefrom has the following structure: 
wherein X and Y are as defined with respect to Formula I. P is an organic group, such as, for example, a polyurethane, preferably having a molecular weight of at least about 15, more preferably about 84-20,000, even more preferably about 3,000-12,000, and a valence of x, wherein x is an integer greater than or equal to 1.
In a more preferred embodiment, a silane-functional polymer of the present invention corresponds to that of Formula IV: 
wherein n and R1-R8 are as defined with respect to Formula II. P is an organic group, such as, for example, a polyurethane, preferably having a molecular weight of at least about 15, more preferably about 84-20,000, even more preferably about 3,000-12,000, and a valence of x, wherein x is an integer greater than or equal to 1.
To form the polymers, an organic group reactive with the secondary amine-functional silanes of the present invention is allowed to react as such. Typically such reactive organic groups contain at least one electrophilic group (e.g., an isocyanate group or an anhydride group).
For example, isocyanate-functional prepolymers (e.g., polyurethanes having reactive isocyanate groups) are reactive with the secondary amine-functional silanes. Such isocyanate-functional prepolymers may be prepared by means well known to those of ordinary skill in the art. These isocyanate-functional prepolymers can then be reacted with secondary amine-functional silanes (with or without a catalyst), as is known in the art. The ingredients are typically allowed to react at temperatures of about 25xc2x0 C. to about 90xc2x0 C.
In a particularly preferred embodiment, the secondary amine-functional silanes are reacted with isocyanate-terminated polyurethane prepolymers. Resulting aminosilane-terminated polymers comprise polyurethane urea segments end-capped with aminosilane groups. The isocyanate-terminated polyurethane prepolymers are prepared by any suitable method, as well known to those of ordinary skill in the art.
In a further embodiment, the secondary amine-functional silanes are useful in preparing silane-terminated polyurethane dispersions. In general, the silane-terminated polyurethane dispersions are prepared by first forming a polyurethane prepolymer by combining a polyisocyanate component with isocyanate reactive compounds. This prepolymer is then dispersed in a water phase that typically provides chain extension and silane termination of the polyurethane prepolymer. In this manner, the polyurethane prepolymer can be end-capped, chain-extended, and dispersed in a water phase.
A summary of basic polymer chemistry and technology which explains and summarizes these reactions and processes as they relate to polyurethanes can be found, for example, in Polyurethanes: Chemistry and Technology, Saunders and Frisch, Interscience Publishers (New York, 1963 (Part I) and 1964 (Part II)). The isocyanate-functional prepolymers may be prepared using a wide range of isocyanate equivalent to hydroxyl equivalent ratios (NCO:OH). Preferred NCO:OH ratios are about 1.25:1 to about 2:1.
While solventless methods of preparation and use may be preferred, the silane-functional polymers may be prepared in and/or used with solvent. For example, solvents such as acetone, butanone, ethyl acetate, toluene, naphtha, N-methylpyrrolidinone, N,N-dimethylformamide, acetonitrile, tetrahydrofuran, and ethylene glycol dimethyl ether can be used for such methods.
The silane-functional polymers may be utilized in the form of a composite and, optionally, in the presence of various additives including moisture-curable catalysts, plasticizers, thixotropic agents, biocides, adhesion promoters, corrosion inhibitors, pigments, fillers, colorants, photostabilizers, antioxidants, perfumes, and other suitable additives.
Useful moisture-curable catalysts include, for example: metal salts and complexes, amines, organic acids, and inorganic acids. Specific examples of useful moisture-curable catalysts include: dibutyltin diacetylacetonate; tetraisopropyl titanate; calcium oxide; N,N,Nxe2x80x2,Nxe2x80x2-tetramethylguanidine; tetrabutylammonium hydroxide; trifluoroacetic acid; dibutyl phosphate; dibutyltin dimethoxide; and 1,3-diazabicycloundec-7-ene.
Useful plasticizers include, for example: benzoates, adipates, phthalates, sebacates, and phosphates. The plasticizers may be present in any suitable amount, although it is generally preferred that the amount of plasticizer not exceed 50% by weight based on total weight of the composition. Specific examples of useful plasticizers include: diisodecyl phthalate, N-ethyl-o, p-toluenesulfonamide, butyl benzyl phthalate, and dipropylene glycol dibenzoate.
Useful thixotropic, or antisagging, agents include, for example: castor waxes, fumed silicas, treated clays, and polyamides. Preferably, the thixotropic agent is essentially non-reactive with the silane functionalities to minimize shelf-life problems.
Useful adhesion promoters include, for example, various silanes, such as those available under the tradenames SILQUEST A-1120, SILQUEST A-187, and SILQUEST A-189 (commercially available from Witco; Endicott, N.Y.).
Fillers may be added to alter, for example, the color, rheology, and ultimate mechanical properties of the silane-functional polymer. Types and use of fillers are well known to those of ordinary skill in the art. Examples of useful fillers: include calcium carbonate, titanium dioxide, carbon black, iron oxide, talc, ceramic microspheres and clay. Ground and/or precipitated calcium carbonates are preferred fillers in applications where low cost and opacity are desirable.
Useful antioxidants and photostabilizers include, for example, those commercially available under the tradenames TINUVIN 770, TINUVIN 327, TINUVIN 1130, and TINUVIN 292 (commercially available from Ciba, Hawthorne, N.Y.). Hindered phenols (e.g., those comprising 2,6-di-tert-butylphenol residues) and hindered amines (e.g., those comprising 2,2,6,6-tetramethylpiperidine residues) are particularly preferred antioxidants.
More than one type of silane-functional polymer may be blended together for certain applications. For example, moisture-curing kinetics of compositions derived from the present silane-functional polymers may be more readily controlled by utilizing various blends of silane-functional polymers. For example, a preferred blend comprises triethoxysilane-functional polymers and trimethoxysilane-functional polymers.
As noted above, silane-functional polymers of the present invention are moisture-curable and provide polymer networks containing siloxane linkages upon curing. Such cured polymers of the present invention have a wide variety of utilities. For example, the polymers are useful in the preparation of coatings, adhesives, sealants, and elastomers.
In one particular application, silane-functional polymers of the present invention are useful as sealants (e.g., automotive seam sealers) for the automotive industry. Automotive seam sealers are typically used in high temperature environments, and as a result, must exhibit thermal stability. In addition, they are typically required to adhere to a wide variety of surfaces, such as cold-rolled steel, primed steel, and galvanized steel. Furthermore, they are typically required to accept paint shortly after application, while still wet, drying to a cured film essentially free of defects (e.g., bubbles or shrinkage that can be measured by the unaided human eye). Due to the minimization or reduction of hydantoin formation in secondary amine-functional silanes of the present invention, shrinkage of the sealants is advantageously minimized. As such, the present secondary amine-functional silanes and polymers derived therefrom are particularly advantageous for use in automobile seam sealers.
Those of ordinary skill in the art can appreciate how to formulate such sealants. For example, a preferred automobile seam sealer contains about 100 parts by weight of a silane-functional polymer; about 5 to about 200 parts by weight of at least one plasticizer; about 1 to about 10 parts by weight of at least one antioxidant; about 0.1 to about 5 parts by weight of at least one moisture-curable catalyst; about 0.1 to about 10 parts by weight of at least one adhesion promoter; about 0.1 to about 10 parts by weight of at least one dehydrator; about 0 to about 500 parts by weight of at least one filler; and about 0 to about 20 parts by weight of at least one thixotropic agent.
Automotive seam sealers typically comprise additives such as those listed above. When the sealer is used in area of the automobile that will be exposed to high temperatures, a combination of two antioxidants comprising a hindered phenolic antioxidant such as those available under the trade designation, BHT (commercially available from Aldrich Chemical, Milwaukee, Wis.) and a hindered amine light stabilizer such as those available under the trade designation, TINUVIN 770 (commercially available from Ciba, Hawthorne, N.Y.) is preferably used. In this embodiment, the weight ratio of hindered amine light stabilizer to hindered phenolic antioxidant is preferably about 1:4.